1. Field of the Invention
The present invention relates to a process for the preparation of cyclic ketones by isomerization of the corresponding epoxides. More specifically, it relates to the rearrangement of the epoxide using an alkali or alkaline-earth halide in the presence of the a polar solvent.
2. Discussion of the Background
According to DE-PS 10 75 601, the isomerization of epoxides to the corresponding cyclic ketones is carried out in diethyl ether with anhydrous halides from group IIA and IIIA elements of the Periodic Table of Elements (designation corresponding to Chemical Abstracts), in particular with magnesium iodide and magnesium bromide. Following removal of the salts by means of a water bath, the ketones are obtained by distillation.
This process has the following disadvantages:
(a) depending on the substrate, the reaction times for a conversion greater than 95% are from 15 to 70 hours; PA1 (b) the use of diethyl ether is very dangerous due to its low flash point, its high volatility, and its tendency to form explosive peroxides; PA1 (c) the catalysts that are used are not recovered and pollute the waste water from the process.
Accordingly, there continues to be a need for a superior method of preparing cyclic ketones from the corresponding epoxides which does not use highly dangerous and flammable solvents, is not polluting and can be conducted on a relatively short time scale.